In a class of diseases known as autoimmune disorders, the body's immune system attacks its own tissues. Some of these diseases are similar to each other. They may involve arthritis and inflammation of arteries in the tissues. People who developed these disorders were previously said to have "connective tissue" or "collagen vascular" disease. We now have names for many specific conditions such as:
When a specific disease cannot be diagnosed, more general terms may be used. These are called undifferentiated systemic rheumatic (connective tissue) diseases or overlap syndromes.
Graf J. Overlap syndromes. In: Firestein GS, Budd RC, Gabriel SE, Koretzky GA, McInnes IB, O’Dell JR, eds. Firestein & Kelley's Textbook of Rheumatology. 11th ed. Philadelphia, PA: Elsevier; 2021:chap 91.
Mims MP. Lymphocytosis, lymphocytopenia, hypergammaglobulinemia, and hypogammaglobulinemia. In: Hoffman R, Benz EJ, Silberstein LE, et al, eds. Hematology: Basic Principles and Practice. 7th ed. Philadelphia, PA: Elsevier; 2018:chap 49.